JP4024374B2 - Discharge lamp lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lighting device that can make a discharge arc of a discharge lamp, particularly an HID lamp (high-intensity discharge lamp), almost straight by acoustic resonance, eliminates color unevenness of the discharge arc due to the cataphoresis phenomenon, and the inclusion is almost at the center of the arc tube. The present invention relates to a discharge lamp lighting device that prevents the discharge arc from adhering around the discharge arc at the portion and suppresses devitrification of the arc tube to extend the life of the discharge lamp.
[0002]
[Prior art]
HID lamps are attracting attention as light sources for outdoor lighting, indoor lighting, especially store lighting because of their high brightness, high efficiency, high color rendering, and long life. Recently, smaller and lower power HID lamps are It is also attracting attention as a light source for equipment and a light source for automobile headlamps.
[0003]
In general, when this type of lamp is lit horizontally, the discharge arc is bent upward due to the influence of convection due to the temperature distribution generated in the arc tube. If the discharge arc is curved, the discharge arc of about 5000K and the upper part of the arc tube are close to each other, so that the temperature of the upper part of the arc tube rises, and the arc tube deteriorates, that is, swells and devitrifies rapidly, and adversely affects the lamp life. It was. In particular, in a small and low-power HID lamp, the distance between the discharge arc and the arc tube is further reduced, so that the discharge arc curvature has a great influence on the lamp life. In addition, since the discharge arc becomes vertically asymmetric when bending occurs, it is necessary to take into account the bending of the discharge arc when optically combined with a reflecting mirror, and the reflecting mirror becomes very complicated. He also had problems.
[0004]
As a method for removing the curvature of the discharge arc, a lighting method using acoustic resonance has been proposed in Japanese Patent Publication No. 7-9835 and Japanese Patent Laid-Open No. 7-14684. According to Japanese Patent Publication No. 7-9835, a current waveform in which an alternating current 52 having a frequency that reduces the influence of convection by acoustic resonance and straightens a discharge arc is superimposed on a direct current 51 as shown in FIG. It teaches that by supplying a lamp, the arc of the discharge arc can be reduced, resulting in a nearly straight discharge arc.
[0005]
Further, according to Japanese Patent Laid-Open No. 7-14684, in the frequency range of 10 kHz to 100 kHz, a frequency and waveform alternating current that excites radial acoustic resonance in the arc tube is supplied to the lamp, and then the frequency of the alternating current is supplied. F _V And radial acoustic wave frequency F _R N · 2F between _V = M · F _R (N, m: integer), F _R = 3.83 C / (2πR) (C: radial sound velocity in the arc tube, R: inner radius of the arc tube) The frequency of the alternating current is selected so that the discharge arc due to the effect of convection It is disclosed that the curvature of can be removed.
[0006]
Acoustic resonance occurs when the lamp is lit at a high frequency, when the frequency inherent to the lamp, which is determined by the shape of the enclosure and arc tube, and the frequency of the periodic change in the power input to the lamp are substantially equal, This phenomenon is caused by the occurrence of the standing wave, which causes instability, extinction of the discharge arc, bursting of the arc tube, and so on, and has conventionally tended to avoid this acoustic resonance. In general, there are three types of acoustic resonance modes in the radial direction, the axial direction, and the circumferential direction, and the method described in Japanese Patent Publication No. 7-9835 and Japanese Patent Laid-Open No. 7-14684 is a method of acoustic resonance in the radial direction. It is a lighting method using resonance.
[0007]
[Problems to be solved by the invention]
However, in the discharge lamp lighting device disclosed in Japanese Examined Patent Publication No. 7-9835, a unidirectional current flows through the discharge lamp. Therefore, although the electric field strength in the discharge space of the discharge lamp changes periodically, a unidirectional electric field is always generated. For this reason, there has been a problem that color unevenness occurs in the discharge arc due to the cataphoresis phenomenon in which the packing is offset.
[0008]
Further, in a lighting device for a discharge lamp according to Japanese Patent Application Laid-Open No. 7-14684, as shown in FIG. 14, the inclusion that exists in a liquid state without evaporating in the arc tube surrounds the discharge arc in the central portion of the arc tube. It adheres almost like a band. This is thought to be due to the fact that the arc becomes linear due to the acoustic resonance in the radial direction, while the density of the inclusions in the central portion of the arc tube increases due to the acoustic resonance in the axial direction, which is another mode of acoustic resonance. .
[0009]
When the inclusion adheres in a strip shape so as to surround the discharge arc in the central portion of the arc tube, the chemical reaction between the quartz glass constituting the arc tube and the inclusion is accelerated at the adhering portion, and strip-like devitrification occurs in the arc tube. As the luminous flux decreases, the lamp life is shortened. In addition, since a normal lamp is used in combination with a reflecting mirror, if strip-like devitrification occurs in the central portion of the arc tube, the efficiency of the instrument combined with the reflecting mirror is reduced.
[0010]
The present invention is intended to solve such problems of the prior art, and its object is to avoid the cataphoresis phenomenon, eliminate the color unevenness of the discharge arc, and light with a substantially straight line with a reduced discharge arc curvature. And it is providing the lighting device which prevents the devitrification of the strip | belt shape of an arc_tube | light_emitting_tube by preventing that an enclosure becomes a strip | belt shape in the center part of an arc_tube | light_emitting_tube, and prolongs a lamp life.
[0011]
[Means for Solving the Problems]
Book The present invention is an apparatus for lighting a discharge lamp having an arc tube that defines a discharge space, and has a waveform having a frequency component of an acoustic resonance frequency that excites a mode for straightening a discharge arc, the center line of the waveform Generating means for generating a first waveform signal having a constant level, and the center line of the first waveform signal alternately change in polarity at a modulation frequency lower than the acoustic resonance frequency. A modulation means for modulating one waveform signal with periodicity and generating a modulation signal, where α is the value from peak to peak of the first waveform signal and β is the effective value of the modulation signal The modulation depth α / β of the arc tube is selected to a value that does not allow the inclusion to adhere to the substantially central portion of the arc tube. The modulation depth α / β is in the range of 0.3 to 0.6. This is a discharge lamp lighting device.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, a sine wave of an acoustic resonance frequency f2 that excites a mode that straightens the discharge arc that is the first waveform signal, and a frequency f1 (400 Hz) that has a waveform in which the polarity alternately changes at a modulation frequency lower than the acoustic resonance frequency f2. ) Shows a combined wave with a rectangular wave.
[0015]
This synthesized wave is a waveform in which a sine wave having an acoustic resonance frequency f2 and a rectangular wave having a frequency f1 are superimposed. The current of the waveform shown in FIG. 1 is supplied to the lamp and is lit horizontally, and the modulation depth α / β (β is the effective of the combined wave is obtained by changing the difference α between the maximum value and the minimum value of the sine wave of the acoustic resonance frequency f2. The results of experimentally determining the magnitude L of the arc of the discharge arc when the value) is changed and the state of attachment of the enclosed material to the arc tube during lighting will be described below.
[0016]
A 35 W metal halide lamp was used for the experiment. FIG. 2A is a diagram showing a method of measuring the curvature L of the discharge arc A, and shows a cross section perpendicular to the electrode axis B at the center between a pair of opposing electrodes 1m and 1n in the light emission interval 1t. The distance between the electrode axis B and the center of the discharge arc A was measured as the curvature L of the discharge arc A.
[0017]
The acoustic resonance frequency f2 of the 35 W metal halide lamp used in the experiment is 150 kHz. FIG. 2 (b) shows the result of determining the curvature L of the discharge arc A. It can be seen that the curvature of the discharge arc gradually decreases as the modulation depth increases, and the magnitude L of the curvature of the discharge arc decreases rapidly at a modulation depth of 0.3 or more. FIG. 2 (c) shows the state of the inclusions attached to the arc tube during lighting. The adhesion state of the inclusions to the arc tube changes almost at the modulation depth of 0.6, and at the modulation depth of 0.6 or less, the inclusions gather under the arc tube due to the influence of gravity, and at the modulation depth of 0.6 or more. It can be seen that the encapsulated material adheres in a strip shape so as to surround the arc at the center of the arc tube.
[0018]
Here, the reason why the inclusion becomes a band at the central portion of the arc tube at a modulation depth of 0.6 or more and the discharge arc becomes straight at a modulation depth of 0.3 or more will be described. It can be estimated that the cause of both is due to acoustic resonance occurring in the arc tube. The acoustic resonance in the axial direction is considered to be the main factor for adhering the inclusions in a strip shape, and the acoustic resonance in the radial direction is the main factor for making the discharge arc straight. The acoustic resonance in the radial direction forms a space in which the discharge arc easily passes in a space near the electrode axis B, and further a space in which the discharge arc hardly passes.
[0019]
For this reason, the discharge arc passes through the space near the electrode axis B, which is easy to pass, and becomes a substantially straight discharge arc. At the same time, axial acoustic resonance also occurs in the arc tube. This axial acoustic resonance sometimes collects the inclusions in a cross section orthogonal to the electrode axis at the center between the electrodes, which is considered to cause the inclusions to adhere in a band shape.
[0020]
The force by which the acoustic resonance moves the enclosure should be proportional to the intensity of the dense waves generated in the arc tube. In the close-packed wave, a periodic change in lamp power is a periodic change in arc temperature, and a periodic change in arc temperature is a pressure change. That is, the force by which the acoustic resonance moves the enclosure and the width of the periodic change of the lamp power are proportional, and if the width of the periodic change of the lamp power is large, the force to move the enclosure increases.
[0021]
When the current shown in FIG. 1 is supplied to the lamp, the larger the difference α between the maximum value and the minimum value of the sine wave at the acoustic resonance frequency f2, that is, the greater the modulation depth α / β, the greater the width of the periodic change in lamp power. It is considered that when the modulation depth α / β is 0.6 or more, a sufficient force is generated to move the inclusion to the central portion of the arc tube, resulting in a band shape.
[0022]
Also, the latter is more effective in moving the gas (light) discharge arc, that is, straightening, and moving the liquid (heavy) enclosure, that is, attaching the belt in the center of the arc tube. Therefore, a force required to straighten a good discharge arc with a relatively small force can be obtained sufficiently with a relatively small modulation depth of 0.3 or more. It is considered that the curvature L of the discharge arc is suddenly reduced at 3 or more.
[0023]
From the above experimental results, by setting the modulation depth to 0.6 or less, it is possible to reduce the curvature of the discharge arc and to prevent the sticking of the inclusions that cause the devitrification of the arc tube, so that the life of the lamp can be extended. . Moreover, since the curvature of the discharge arc can be further reduced by setting the modulation depth in the range of 0.3 to 0.6, the effect of extending the life is greater.
[0024]
1 is applied to the lamp, the polarity of the lamp current changes with the period of the rectangular wave of 400 Hz, and the polarity of the electric field generated in the discharge space changes periodically. Change. Therefore, the cataphoresis phenomenon can be prevented, and the discharge arc color unevenness can be prevented.
[0025]
3 shows a sine wave of an acoustic resonance frequency f2 that excites a mode that straightens the discharge arc, which is the first waveform signal, and a frequency f3 that has a waveform in which the polarity alternately changes at a modulation frequency lower than the acoustic resonance frequency f2. A composite wave with a triangular wave is shown. This synthesized wave has a waveform in which a sine wave having an acoustic resonance frequency f2 and a triangular wave having a frequency f3 are superimposed.
[0026]
Even if a current having a modulation depth of 0.6 or less is supplied to the lamp in the waveform shown in FIG. 3, the discharge arc is similarly reduced, and it is possible to prevent the adhering band-like attachment causing the devitrification of the arc tube. Furthermore, since the polarity of the electric field generated in the discharge space changes with a period determined by the frequency f3, the cataphoresis phenomenon can be prevented.
[0027]
Here, the first waveform signal is a sine wave of the acoustic resonance frequency f2 that excites the mode that straightens the discharge arc, but the waveform includes the frequency component of the acoustic resonance frequency f2 that excites the mode that straightens the discharge arc. For example, a triangular wave or a sawtooth wave may be used. In addition, if a sine wave with frequency modulation that changes the frequency with a predetermined period and width is used, the change / variation in the acoustic resonance frequency that excites the mode that straightens the discharge arc caused by the change / variation in the lamp characteristics over time. Can absorb.
[0028]
In addition, although a composite wave with a rectangular wave of frequency f1 or a triangular wave of frequency f3, which is a waveform whose polarity alternately changes at a modulation frequency lower than the acoustic resonance frequency f2, is shown as an example, other waveforms such as a sine wave, A similar effect can be obtained if it is a combined wave with a waveform whose polarity alternately changes at a frequency having an upper limit of the acoustic resonance frequency f2 for exciting a mode that straightens the discharge arc, such as a staircase wave or a sawtooth wave. Further, the waveform may include a slight DC component as long as the polarity is changed, and may be a positive / negative asymmetric waveform. In short, the waveform may be any waveform that can avoid the cataphoresis phenomenon so that the electric field in the discharge space of the discharge lamp does not become one direction.
[0029]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 4 shows a first embodiment for a 35 W metal halide lamp. In FIG. 4, reference numeral 1 denotes the 35 W metal halide lamp described above, which is a discharge lamp in which mercury and a metal halide (Sc—Na system) are sealed in an arc tube defining a discharge space.
[0030]
Reference numeral 2 denotes lighting means for supplying a current of a predetermined waveform to the 35 W metal halide lamp 1 for lighting. The lighting means 2 is a first waveform signal having a frequency component of an acoustic resonance frequency for exciting a mode for straightening a discharge arc. A sine wave generating circuit 3 that generates a 150 kHz sine wave as a generating means, and a rectangular wave generator that generates a 400 Hz rectangular wave as a polarity changing power source that outputs a waveform whose polarity changes at a frequency up to the acoustic resonance frequency. The circuit 4 is composed of a synthesis circuit 5 that synthesizes the output of the sine wave generation circuit 3 and the output of the rectangular wave generation circuit 4.
[0031]
FIG. 5 shows waveforms of respective parts of the first embodiment configured as described above.
FIG. 5A shows an output waveform of the rectangular wave generating circuit 4, which is a 400 Hz rectangular wave. FIG. 5B shows an output waveform of the sine wave generation circuit 3, which is a 150 kHz sine wave. FIG. 5C shows an output waveform of the synthesis circuit 5 in which the output of the sine wave generation circuit 3 and the output of the rectangular wave generation circuit 4 are superimposed, and the rectangular wave generation circuit has a modulation depth of 0.6 or less. 4 and the output of the sine wave generation circuit 3 are set, and the waveform of FIG. 5C is applied to the 35 W metal halide lamp 1.
[0032]
As described above, according to the first embodiment, the acoustic resonance frequency sine wave (150 kHz) and the 400 Hz rectangular wave for exciting the 35 W metal halide lamp 1 in the mode in which the discharge arc shown in FIG. Since a combined wave with a modulation depth of 0.6 or less can be applied, a straight discharge arc with no color unevenness can be realized and a band-like adhesion of the inclusion can be prevented.
[0033]
FIG. 6 shows a second embodiment. In FIG. 6, reference numeral 1 denotes a 35 W metal halide lamp similar to that of the first embodiment. Reference numeral 12 denotes lighting means for supplying a predetermined waveform to the 35 W metal halide lamp 1 for lighting, and the lighting means 12 is a first waveform signal generating means having a frequency component of an acoustic resonance frequency for exciting a mode for straightening the arc. A high-frequency power supply 17 that generates a certain 150 kHz sine wave, a modulation means 13 that modulates the output of the high-frequency power supply 17 so that the polarity alternately changes at a modulation frequency lower than the acoustic resonance frequency, and the discharge of the 35 W metal halide lamp 1 And starting means 15 for applying a sufficiently high voltage for starting.
[0034]
The modulation means 13 includes a DC power supply 16 that outputs a DC signal whose instantaneous value does not change with time, a superposition circuit 18 that superimposes the output of the high-frequency power supply 17 on the output of the DC power supply 16, and an output from the superposition circuit 18 as an acoustic signal. The rectangular wave conversion circuit 14 is an inverter circuit that alternately changes the polarity at a modulation frequency lower than the resonance frequency. FIG. 7 shows waveforms of respective parts of the second embodiment configured as described above.
[0035]
FIG. 7A shows an output current waveform of the DC power supply 16. The DC power supply 16 includes a DC power supply 19, a transistor 20, a diode 21, a choke coil 22, and a capacitor 23 to form a step-down chopper circuit. The control circuit 27 calculates lamp power from the signal corresponding to the lamp voltage detected at 25 and the signal corresponding to the lamp current detected at the resistor 26, and the on / off ratio of the transistor 20 is varied so that the lamp power is constant at 35W. A DC waveform whose instantaneous value does not change with time is output.
[0036]
FIG. 7B shows an output current waveform of the high-frequency power source 17. The high-frequency power source 17 modulates the output current of the sine wave power source 28 that outputs a sine wave with an acoustic resonance frequency of 150 kHz and the sine wave power source 28 to a depth of 0.6 or less. And a sine wave current having an acoustic resonance frequency is output.
[0037]
FIG. 7C shows an output current waveform of the superposition circuit 18, which is composed of a choke coil 30 and a capacitor 31, and the capacitor 31 prevents the output current of the DC power source 16 from flowing into the high frequency power source 17. The DC cut is performed, and the choke coil 30 is used to cut the high frequency so that the output current of the high frequency power supply 17 does not flow into the DC power supply 16. Output superimposed DC.
[0038]
FIG. 7D shows an output current waveform of the rectangular wave conversion circuit 14. The rectangular wave conversion circuit 14 includes transistors 32, 33, 34, and 35 and a drive circuit 36. A 35W metal halide is produced by alternately generating a period in which the transistors 32 and 35 are turned on and a period in which the transistors 33 and 34 are turned on to convert a direct current superimposed with a sine wave of the acoustic resonance frequency, which is the output of the superposition circuit 18, into an alternating current of 400 Hz. Supply to lamp 1.
[0039]
As described above, according to the second embodiment, when the 35 W metal halide lamp 1 is lit with the high voltage from the starting means 15, the discharge arc is then applied at a modulation depth of 0.6 or less as shown in FIG. Since a combined wave current of a sine wave having an acoustic resonance frequency (150 kHz) that excites a straightening mode and a rectangular wave having a frequency equal to or lower than the acoustic resonance frequency (400 Hz) can be supplied, the discharge arc has no color unevenness. The discharge arc can be realized, and the adhering band-like adhesion can be prevented. The modulation depth can be freely varied by changing the output voltage of the sine wave power supply 28.
[0040]
FIG. 8 shows a third embodiment of the present invention. In FIG. 8, 1 is a 35 W metal halide lamp which is a discharge lamp similar to the first and second embodiments. 40 is a lighting means for starting and lighting the 35 W metal halide lamp 1, and generates a first waveform signal that outputs a direct current on which a waveform having a frequency component of an acoustic resonance frequency that excites a mode for straightening a discharge arc is superimposed. DC power source 41 as means, a high frequency power source 17 that generates a sine wave of 150 kHz, a modulation unit 13 that modulates the output of the high frequency power source 17 so that the polarity alternately changes at a modulation frequency lower than the acoustic resonance frequency, and the direct current A rectangular wave conversion circuit 14 that is an inverter circuit that changes the polarity of the output of the power supply 41 at a frequency that has an acoustic resonance frequency as an upper limit, and a starter 15 that applies a high voltage sufficient to start the discharge of the 35 W metal halide lamp 1. It consists of and.
[0041]
The rectangular wave conversion circuit 14 and the starter 15 have the same configuration as that of the second embodiment. The difference from the second embodiment is the configuration of a DC power supply 41 that is a first waveform signal generating means having a frequency component of an acoustic resonance frequency that excites a mode that straightens the discharge arc. The configuration and operation will be described.
[0042]
The direct current power source 41 comprises a step-down chopper circuit composed of the direct current power source 42, the transistor 43 as a switching element, the diode 44, the choke coil 45 and the capacitor 46, and a signal corresponding to the lamp voltage detected by the resistors 47 and 48 and the resistor 49. The control circuit 50 calculates the lamp power from the signal corresponding to the detected lamp current, and the on / off ratio of the transistor 43 is varied so that the lamp power is constant at 35 W. The acoustic resonance frequency for exciting the straight mode is set to 150 kHz, and the filter circuit constituted by the choke coil 45 and the capacitor 46 has a characteristic that the 150 kHz component is not cut and the modulation depth is 0.6 or less. By setting the value, the output current waveform of the DC power supply 41 is 150 kHz. Can output periodically fluctuating modulation depth 0.6 DC.
[0043]
An output current waveform of the DC power supply 41 of the third embodiment configured as described above is shown in FIG. 9A, and an output current waveform of the rectangular wave conversion circuit 14 is shown in FIG. 9B.
[0044]
Similar to the first and second embodiments, the 35 W metal halide lamp 1 has a modulation depth of 0.6 or less and a waveform having a frequency component of an acoustic resonance frequency (150 kHz) that excites a mode that straightens the discharge arc. Since a combined wave current with a rectangular wave having a frequency equal to or lower than the acoustic resonance frequency (400 Hz) can be supplied, it is possible to realize a straight discharge arc with no color unevenness in the discharge arc and to prevent adhesion of the inclusions in a band shape.
[0045]
In addition, the choke coil 45 and the capacitor 46 are set to predetermined values, and the on / off frequency of the transistor 43 is set to 150 kHz, which is a frequency at which the discharge arc can be straightened at an acoustic resonance frequency. Since a predetermined modulation depth can be added, the configuration of the lighting means is simplified.
[0046]
FIG. 10 shows a fourth embodiment of the present invention. In FIG. 10, the third embodiment is different from the third embodiment in that it has a modulation depth control means 51 that detects the adhesion state of the enclosure to the arc tube and changes the modulation depth α / β according to the adhesion state. The capacitor 53 in the DC power source 52, which is a means for generating a first waveform signal that outputs a DC having a waveform having a frequency component of an acoustic resonance frequency that excites a mode that straightens the discharge arc, is a variable capacity type. Since other configurations are the same, description thereof is omitted.
[0047]
The modulation depth control means 51 is arranged in the vicinity of the 35 W metal halide lamp, and the light receiving means 54 which is a detection means for detecting the state of the lit inclusion, that is, whether or not it is a band, and the signal from the light receiving means 54 And a modulation depth control circuit 58 that changes the capacitance and changes the modulation depth α / β. The light receiving means 54 is disposed so as to receive the local light transmitted through the portion where the encapsulated material becomes a band, that is, the central portion of the arc tube.
[0048]
The operation of the discharge lamp lighting device of the fourth embodiment configured as described above will be described below. First, a method for detecting whether or not the inclusion is in a band shape will be described.
[0049]
Light emitted from the discharge arc passes through the arc tube, but when the arc tube enclosure adheres in a band shape, reflection and absorption of light by the enclosure occur at that portion, and the light transmission spectral characteristics change locally. To do. That is, there is light with a wavelength that is significantly different between when the inclusion is attached and when it is not attached. If the light receiving means 14 is configured so that this change can be detected, the state of the inclusion can be detected.
[0050]
Specifically, as shown in FIG. 11, the photodiode 55, the filter 56, and the lens 57 constitute the light receiving means 54, and the local light at the portion where the encapsulated material becomes a band is collected by the lens 57, and the filter Light is received by the photodiode 55 through 56.
[0051]
For example, if the inclusion is a Sc-Na iodide, the color of the inclusion is light yellow and has the property of absorbing blue light. Therefore, if the encapsulated material has a band shape, blue light is greatly reduced in the light transmitted therethrough. That is, it is possible to detect whether the encapsulated material is band-like or not based on the amount of blue light, and a blue transmission filter is used as the filter 56 in order to detect this change in blue light.
[0052]
With this configuration, when the encapsulated material has a band shape, the light input to the light receiving means 54 contains almost no blue light, so that almost no light is input to the photodiode 55, and the light receiving means 54. Is almost zero, and the modulation depth control circuit 58 determines that the inclusion is in a band shape.
[0053]
On the other hand, when the inclusion is not in the form of a band, the light input to the light receiving means 54 includes blue light, so that the light that has passed through the filter 56 is input to the photodiode 55 and received by the light receiving means 54. Outputs a signal proportional to the amount of light input to the photodiode 55 to the modulation depth control circuit 58, and the modulation depth control circuit 58 determines that the iodide is not in the form of a band if this signal is a predetermined value. To do.
[0054]
The relationship between the modulation depth and the capacitance of the capacitor 53 is as shown in FIG. 12, and the modulation depth decreases as the capacitance of the capacitor increases. Therefore, the modulation depth control circuit 58 controls the modulation depth by increasing the capacitance of the capacitor 53 to decrease the capacitance of the capacitor 53 to increase the modulation depth and increasing the capacitance of the capacitor 53 to decrease the modulation depth.
[0055]
As described above, according to the fourth embodiment, the light receiving means 54 detects the state of the enclosed object while the 35 W metal halide lamp 1 is lit, and the modulation depth control circuit 58 varies the modulation depth, thereby The 35 W metal halide lamp 1 can be lit at a modulation depth where the curvature of the discharge arc is the smallest in the region where is not strip-shaped. Further, it is possible to absorb the variation in the modulation depth at which the inclusion becomes a band due to the manufacturing intersection of the 35 W metal halide lamp 1 and the change over time.
[0056]
In the above embodiment, the discharge lamp is a 35 W metal halide lamp. However, other lamps may be used as long as the inclusion is in a liquid state in the arc tube during lighting.
[0057]
The rectangular wave generating circuit 4 generates a standard rectangular wave in the present embodiment, but may be configured to generate a trapezoidal wave having a slope at the rising and falling edges of the waveform. The structure which can generate | occur | produce may be sufficient. Similarly, the rectangular wave conversion circuit 14 may have another configuration as long as it can convert into a substantially rectangular wave. Further, the rectangular wave generating circuit 4 and the rectangular wave converting circuit 14 are polar at a frequency having an upper limit of an acoustic resonance frequency that excites a mode for straightening a discharge arc, such as a sine wave, a triangular wave, a staircase wave, and a saw wave other than a substantially rectangular wave. It is possible to generate a waveform that alternately changes, a waveform that includes some DC component, as long as the polarity is changed, and a waveform that is asymmetric between positive and negative may be used. In short, the waveform may be any waveform that can avoid the cataphoresis phenomenon so that the electric field in the discharge space of the discharge lamp does not become one direction.
[0058]
Furthermore, although the frequency of the rectangular wave generation circuit 4 and the rectangular wave conversion circuit 14 is 400 Hz, any frequency may be used as long as the upper limit is the acoustic resonance frequency that excites the mode for straightening the discharge arc.
[0059]
Further, the sine wave generating circuit 3 and the high frequency power supply 17 are configured to generate a 150 kHz sine wave. However, for example, a triangular wave, a sawtooth wave, or the like may be used as long as it has a frequency component of the acoustic resonance frequency. The same applies to the sine wave power supply 28.
[0060]
In addition, when an FM modulation function is added to the sine wave generation circuit 3 and the sine wave power supply 28 so that the frequency of the sine wave generated can be varied with a predetermined period and width, a discharge arc generated due to a change and variation in lamp characteristics with time is generated. It can absorb changes and variations in the acoustic resonance frequency that excites the straightening mode. Similarly, if the on / off frequency of the transistor 43 of the third embodiment can be FM-modulated by a signal from the control circuit 50, the same effect can be obtained.
[0061]
The high frequency power supply 17 is constituted by a sine wave power supply 28 and a choke coil 29, and the output current of the sine wave power supply 28 is limited to the predetermined modulation depth by the impedance of the choke coil 29. A resistor / capacitor and their combined configuration may be used.
[0062]
Further, although the DC power supply 16 that outputs a waveform whose instantaneous value does not change with time is configured by a step-down chopper circuit, the same configuration is possible with other circuit systems such as a step-up chopper circuit and an inverting chopper circuit.
[0063]
In addition, the control circuits 27 and 50 are configured to control the on / off ratio of the transistors 20 and 43 so that the lamp power is constant at a rated value of 35 W. Control may be performed so that the above power is supplied, or a configuration in which lamp characteristics are variably controlled, such as dimming control, may be used.
[0064]
Further, although the superposition circuit 18 is constituted by the choke coil 30 and the capacitor 31, it goes without saying that other configurations may be adopted.
[0065]
Further, the DC power supply 41 may be configured by other circuit methods such as a step-up chopper circuit, an inverting chopper circuit, or a forward converter circuit as long as it can output a DC with a waveform having a frequency component of the acoustic resonance frequency.
[0066]
In addition, although a transistor is used as the switch element, other elements such as an FET, a thyristor, and an IGBT may be used.
[0067]
In addition, the light receiving means 54 for detecting the state of the enclosed material during lighting of the 35 W metal halide lamp 1 is constituted by the photodiode 55, the filter 56, and the lens 57, but the filled material is not in a band shape during lighting. For example, a 35 W metal halide lamp 1 can be imaged with a CCD camera and detected by image processing. The filter 56 may be another filter as long as it can detect light having a wavelength that is significantly different between when the inclusion is attached and when it is not. Needless to say, the filter 56 needs to be changed if the enclosed matter is different.
[0068]
【The invention's effect】
As described above, according to the present invention, a waveform having a frequency component of an acoustic resonance frequency that excites a mode in which a discharge arc is straight and a waveform whose polarity alternately changes at a frequency with the acoustic resonance frequency as an upper limit. By turning on the discharge lamp with a composite wave and selecting the modulation depth to a value that does not cause the inclusions to adhere to the center of the arc tube, a straight discharge arc with no color unevenness can be realized and the lighting is on. In addition, it is possible to prevent the encapsulated material from forming a belt-like shape at the central portion of the arc tube, thereby extending the life of the discharge lamp.
[Brief description of the drawings]
FIG. 1 is a diagram showing a combined wave of a sine wave having an acoustic resonance frequency f2 and a rectangular wave having a frequency f1 for exciting a mode in which a discharge arc is straightened.
FIG. 2A is a diagram showing the curvature of a discharge arc in a lamp.
(B) The figure which shows the change of the distance of an electrode axis | shaft and discharge arc center when changing the modulation depth.
(C) Schematic diagram showing the state of attachment of the inclusion when the modulation depth is changed
FIG. 3 is a diagram showing a combined wave of a sine wave having an acoustic resonance frequency f2 and a triangular wave having a frequency f3 for exciting a mode for straightening a discharge arc.
FIG. 4 is a configuration diagram of a discharge lamp lighting device according to the first embodiment of the present invention.
5A is an output waveform diagram of the rectangular wave generation circuit 4. FIG.
(B) Output waveform diagram of sine wave generation circuit 3
(C) Output waveform diagram of synthesis circuit 5
FIG. 6 is a configuration diagram of a discharge lamp lighting device according to a second embodiment of the present invention.
7A is an output waveform diagram of the DC power supply 16. FIG.
(B) Output waveform diagram of the high-frequency power supply 17
(C) Output waveform diagram of superposition circuit 18
(D) Output waveform diagram of rectangular wave conversion circuit 14
FIG. 8 is a configuration diagram of a discharge lamp lighting device according to a third embodiment of the present invention.
9A is an output waveform diagram of the DC power supply 41. FIG.
(B) Output waveform diagram of the rectangular wave conversion circuit 14
FIG. 10 is a configuration diagram of a discharge lamp lighting device according to a fourth embodiment of the present invention.
FIG. 11 is a block diagram of the light receiving means 54 for detecting the state of the encapsulated object during lighting.
FIG. 12 is a diagram showing the relationship between the positive capacitance of the capacitor 53 and the modulation depth.
FIG. 13 is a lamp current waveform diagram when a discharge lamp is lit by a conventional discharge lamp lighting device.
FIG. 14 is a schematic diagram showing an attached state of an inclusion when a discharge lamp is lit with a conventional discharge lamp lighting device.
[Explanation of symbols]
1 35W metal halide lamp
2 lighting means
3 Sine wave generator
4 Rectangular wave generation circuit
5 Synthesis circuit
12 lighting means
13 Modulation means
14 Rectangular wave conversion circuit
15 Starting means
16 DC power supply
17 High frequency power supply
18 Superposition circuit
40 lighting means
41 DC power supply
51 Modulation depth control means
52 DC power supply
54 Light receiving means
58 Modulation depth control circuit
59 Lighting means

Claims (5)

An apparatus for lighting a discharge lamp having an arc tube that defines a discharge space,
Generating means for generating a first waveform signal having a frequency component of an acoustic resonance frequency for exciting a mode for straightening a discharge arc, the center line of the waveform being held at a constant level;
Modulation that modulates the first waveform signal with periodicity and generates a modulation signal such that the polarity of the center line of the first waveform signal alternately changes at a modulation frequency lower than the acoustic resonance frequency. Means,
When the value from the peak to the peak of the first waveform signal is α and the effective value of the modulation signal is β, the modulation depth α / β is not substantially attached to the central portion of the arc tube. A discharge lamp lighting device that is selected as a value and the modulation depth α / β is in the range of 0.3 to 0.6 . . 2. The discharge lamp lighting device according to claim 1, wherein the acoustic resonance frequency is determined by the speed of sound in the discharge space medium of the discharge lamp and the length of the discharge space intersecting the discharge arc. The discharge lamp lighting device according to claim 1 or 2, wherein the discharge lamp contains at least a metal halide or mercury as an enclosure. The discharge according to any one of claims 1 to 3 , further comprising a modulation depth control means that detects a state of adhesion of the inclusion to the arc tube and changes the modulation depth α / β according to the state of adhesion. Lamp lighting device. 5. The discharge lamp lighting device according to claim 4, wherein the modulation depth control means detects the light output of the discharge lamp.

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